Make DCD conditional on PHP 8.1+ to fix old PHP CI

Move DCD rules.neon include to ignore-by-php-version.neon.php so it
only loads on PHP >= 8.1. Move inline @phpstan-ignore for
BleedingEdgeToggle to neon config. Add reportUnmatched: false to all
DCD-specific ignores.

Co-Authored-By: Claude Code

Author: janedbal

build/ignore-by-php-version.neon.php

@@ -8,6 +8,7 @@
 }
 if (PHP_VERSION_ID >= 80100) {
 	$includes[] = __DIR__ . '/baseline-8.1.neon';
+	$includes[] = __DIR__ . '/../vendor/shipmonk/dead-code-detector/rules.neon';
 } else {
 	$includes[] = __DIR__ . '/enums.neon';
 	$includes[] = __DIR__ . '/readonly-property.neon';

build/phpstan.neon

@@ -4,7 +4,6 @@ includes:
 	- ../vendor/phpstan/phpstan-phpunit/extension.neon
 	- ../vendor/phpstan/phpstan-phpunit/rules.neon
 	- ../vendor/phpstan/phpstan-strict-rules/rules.neon
-	- ../vendor/shipmonk/dead-code-detector/rules.neon
 	- ../conf/bleedingEdge.neon
 	- ../phpstan-baseline.neon
 	- ../phpstan-baseline.php
@@ -81,11 +80,17 @@ parameters:
 		-
 			identifier: shipmonk.deadMethod
 			message: '#^Unused .*?Factory::create#' # likely used in DIC
+			reportUnmatched: false
+		-
+			identifier: shipmonk.deadMethod
+			message: '#^Unused PHPStan\\DependencyInjection\\BleedingEdgeToggle::isBleedingEdge#' # kept for future use
+			reportUnmatched: false
 		-
 			identifier: shipmonk.deadMethod
 			paths:
 				- ../tests/PHPStan/Tests
 				- ../tests/e2e
+			reportUnmatched: false
 		-
 			identifier: shipmonk.deadConstant
 			paths:
@@ -127,6 +132,7 @@ parameters:
 			reportUnmatched: false
 		-
 			rawMessage: 'Property PHPStan\Command\CommandHelper::$reservedMemory is never read' # intentional
+			reportUnmatched: false
 	reportStaticMethodSignatures: true
 	tmpDir: %rootDir%/tmp
 	stubFiles:

src/DependencyInjection/BleedingEdgeToggle.php

@@ -7,7 +7,7 @@ final class BleedingEdgeToggle
 
 	private static bool $bleedingEdge = false;
 
-	public static function isBleedingEdge(): bool // @phpstan-ignore shipmonk.deadMethod (kept for future use)
+	public static function isBleedingEdge(): bool
 	{
 		return self::$bleedingEdge;
 	}